1. Field of the Invention
The present invention relates to a driving mechanism employed in an optical device such as a still camera or a video camera, and more specifically, it relates to a driving mechanism that communicates the driving power generated at a drive source to an object to be driven by utilizing a plurality of gears.
2. Description of the Related Art
Still cameras and video cameras are provided with various types of driving mechanisms including a lens driving mechanism, a film feed mechanism and a tape feed mechanism. These driving mechanisms are normally provided with a motor constituting a drive source and communicates the driving power of the motor to the object to be driven (such as a lens, film or videotape) via a speed-reducing gear train constituted of a plurality of gears. As a result, noise is generated at the gear meshing portions and the shaft rotation supporting portions as well as the motor drive noise during an operation of such a driving mechanism, and the noise can be a problem. Among the various types of noise, the noise occurring at the gear meshing portions, and more specifically the impact noise resulting from the collision of tooth flanks of the gears and the rubbing noise that occurs when the tooth flanks rub against each other, are particularly problematic. The noise tends to sound unusually loud in a quiet environment and irritates people in the vicinity as well as the photographer when the camera or the like is used in a quiet and serious situation.
An object of the present invention is to provide a driving mechanism of an optical device that achieves a reduction in the noise generated at a gear meshing portion.
In order to achieve the object described above, the driving mechanism of an optical device according to the present invention that communicates the driving force generated at a drive source to an object to be driven includes, at least, a gear having a low bending elastic modulus within the range of 10 kgf/mm2xcx9c100 kgf/mm2 manufactured by using at least one of; polyester, polyamide and polyacetals and a gear having a high bending elastic modulus within a range of 50 kgf/mm2xcx9c1000 kgf/mm2 manufactured by using at least one of; polyester, polyamide and polyacetals, and the gear having the low bending elastic modulus and the gear having the high bending elastic modulus are meshed with each other.
It is desirable to set the bending elastic modulus of the gear having the high bending elastic modulus within the range of 50 kgf/mm2xcx9c700 kgf/mm2 or within the range of 50 kgf/mm2xcx9c300 kgf/mm2.
Either the gear having the low bending elastic modulus or the gear having the high bending elastic modulus may mesh with a gear which rotates at the highest speed among the plurality of gears in the driving mechanism. The gear having the low bending elastic modulus may mesh with the gear rotating at the highest speed. The gear having the high bending elastic modulus itself may be a gear rotating at the highest speed among the plurality of gears.
In addition, either the gear having the low bending elastic modulus or the gear having the high bending elastic modulus described above may have a durometer hardness (type D) of 45xcx9c55. In such a case, it is preferable to set the durometer hardness (type D) of the gear having the low bending elastic modulus at 40xcx9c55 and to set the durometer hardness (type D) of the gear having the high bending elastic modulus at 45xcx9c60.
The driving mechanism of an optical device according to the present invention may also achieve the object by including at least a plurality of gears manufactured by using at least one of; polyester, polyamide and polyacetals, and each having a durometer hardness (type D) of 45xcx9c55, which mesh with each other. In this driving mechanism, the plurality of gears may include a gear that rotates at the highest speed among the plurality of gears in the driving mechanism or a gear that meshes with the gear rotating at the highest speed.